Transponder/EFIS D100 altitude discrepency

[Dick_B]

I have a EFIS D100 with grey code converter module hooked to a Becker BXP6401-2-(01) transponder. There is a 280 foot discrepency between the two after getting radar verification (transponder lower than EFIS). How do I correct this?

 

[dynonsupport]

Are you aware they are only supposed to match when the D100 is set to 29.92?

If so, you really need to go to a avionics shop to have this looked at. The discrepancy is likely not fixed- it will change as you change altitude. A good shop can look at a few different altitudes and tell you which wire(s) are broken.

When was your last transponder check? Was it working then?

 

[Dick_B]

Currently located at an uncontrolled field and cannot travel to a avionics shop until experimental restrictions are flown off. While performing test flights asked for altitude readouts from nearby approach control facility.

 

[dynonsupport]

So you are aware, it is illegal to operate your transponder until it's checked. You must leave it off. FAR 91.217 and 91.413.